This invention relates in general to conveyor systems and in particular to an improved transfer system for use in transferring packages between a conveyor system and an accumulator.
Conveyors are well known devices which are commonly used in production line situations to transport packages from one location to another. For example, a conveyor may be used to transport packages of a product from an upstream filling station, wherein the packages are filled with the product and sealed, to a downstream packaging station, wherein the sealed packages are packaged into larger shipping packages. Many conveyor system structures are known in the art for accomplishing this basic function.
Usually, the conveyor system is designed to provide a continuous flow of packages from the upstream station on the production line to the downstream station. However, it occasionally becomes necessary to halt this continuous flow of packages. For example, the flow of packages may need to be stopped because one or more of the packages becomes jammed in the production line and must be cleared. Alternatively, the flow of packages may need to be halted because the downstream processing equipment is temporarily unable to accept the continued flow of packages. To accommodate this, some known conveyor systems are provided with a control system which simply ceases the flow of packages through the entire conveyor system when this occurs. This is usually undesirable because it requires that the upstream equipment on the production line cease operation until the problem in the conveyor system or in the downstream processing equipment is corrected.
To address this problem, it is known to provide one or more accumulators midstream within a conveyor system. An accumulator is a device which is typically located between first and second individual conveyors in a conveyor system. When the production line is operating normally, the accumulator receives products from the first conveyor and merely transports them therethrough to the second conveyor. However, when a problem occurs in the downstream portion of the production line, such as described above, the accumulator receives products from the first conveyor and temporarily stores them therein until the problem is corrected. Thus, the accumulator functions to temporarily prevent the flow of the packages downstream thereof, while permitting the upstream portion of the production line to continue, at least temporarily, in normal operations.
Many different accumulator structures are known in the art. One type of accumulator structure is known as a horizontal accumulator. A typically horizontal accumulator includes a plurality of horizontally spaced, parallel storage paths. One or more entrance gates are provided for directing the flow of products from the first conveyor to one of the storage paths as necessary. In this manner, the flow of products downstream is temporarily prevented. When it is desired to resume the flow of products downstream of the horizontal accumulator, one or more exit gates are opened so as to direct the stored products from the storage paths into the second conveyor. While horizontal accumulators of this general type are effective for temporarily preventing the flow of products therethrough, they have been found to be inefficient because of their physical size. Specifically, the parallel storage paths of these horizontal accumulators occupy an undesirable large amount of floor space in the facility in which they are used.
To minimize this floor space problem, a second type of accumulator structure, known as a vertical accumulator, has been developed. A typical vertical accumulator includes a plurality of vertically spaced, parallel storage paths. Packages passing through the vertical accumulator are received from the first conveyor and stored in groups on shelves. When a first shelf is filled with a plurality of packages, it is elevated above the vertical height of the first and second conveyors to permit a second shelf to be filled in a similar manner. When it is desired to return the stored products to the conveyor system, the shelves are sequentially lowered to permit the packages to be fed to the second conveyor. Thus, it can be seen that vertical accumulators occupy a relatively small amount of floor space in the facility in which they are used and, therefore, are generally preferable to the horizontal accumulators described above.
To facilitate the use of accumulators, a transfer system is provided to transfer the packages from the conveyor to the accumulator and from the accumulator back to the conveyor. In some accumulators, the upper surface of the accumulator shelf to be loaded (or unloaded) is positioned directly adjacent the upper surface of the conveyor, and a mechanical pusher or other device is provided to push the packages from the conveyor to the accumulator shelf (or from the accumulator shelf to the conveyor). Although effective for relatively large packages, such a pusher transfer system requires equipment both on the conveyor and in the accumulator to effect movement in both directions. Furthermore, pusher transfer systems cannot handle relatively small or delicate packages and are relatively slow to cycle during operation because the shelf cannot be moved until the mechanical pusher has been fully retracted after moving the packages onto (or off of) the accumulator shelf.
In other accumulators, each accumulator shelf is formed from a plurality of elongated fingers that are sequentially interleaved with the rollers of the conveyor. To transfer packages from the conveyor to the accumulator, one shelf of fingers is raised to lift the packages off the rollers of the conveyor for storage, while the fingers of the next empty shelf are positioned between the rollers of the conveyor. This interleaved finger transfer system is effective for handling relatively small and delicate packages. However, because the fingers of the accumulator shelves are interleaved between the rollers of the conveyor and are sized to handle relatively large loads, the rollers of the conveyor must be spaced apart from one another by a relatively large distance. This relatively large roller spacing prevents this type of system from handling packages that are extremely small or extremely delicate. The distance between adjacent centers of the roller of the conveyor is one factor which determines the size of packages which can be conveyed thereon. Typically, the minimum size of a package that can be moved on a conveyor is about two to three times the distance between adjacent centers of the rollers. Thus, it would be desirable to provide an improved structure for a transfer system that is capable of quickly moving extremely small packages onto and off of an accumulator shelf.